Hasil untuk "By period"

A. Verdecchia, S. Francisci, H. Brenner et al.

D. Duffie, Leandro Saita, Ke Wang

R. Stellingwerf

M. Hills, London SW75BD, P. Armitage

S. Ge, Chih-hao Yang, K. Hsu et al.

A. James, M. Jamison, L. Brancazio et al.

T. Erdogan

A. Shrestha, C.P Wake, P. Mayewski et al.

I. Jones, P. Chandra, P. Dazzan et al.

J. Salas, J. Obeysekera

N. Vandenberghe, F. Hilgen, R. Speijer

Yang Yang, K. Land

H. Kamel, B. Navi, N. Sriram et al.

A. Khodaei

J. Chaput, V. Carson, C. Gray et al.

Physical inactivity and childhood obesity are well-recognized public health concerns that are associated with a range of adverse health outcomes. Historically, the benefits of physical activity (e.g., moderate-to-vigorous physical activity—MVPA) to overall health have dominated discussions and emerging evidence indicates that a broader, more integrated approach is needed to better understand and address current public health crises. Existing guidelines for children and youth around the world only focus on MVPA, and recently sedentary behavior, despite an accumulating body of evidence showing that light-intensity physical activity (LPA) such as walking can provide important health benefits. Furthermore, there is accumulating support for the importance of adequate sleep and that these behaviors moderate the health impact of each other. Ignoring the other components of the movement continuum (i.e., sleep, sedentary time, LPA) while focusing efforts exclusively on MVPA (accounting for <5% of the time in a 24 h period) limits the potential to optimize the health benefits of movement behaviors. In order to address this limitation, experts in Canada are currently developing the world’s first Integrated 24 Hour Movement Behaviour Guidelines for Children and Youth to help advance an integrated healthy active living agenda that has the potential to significantly improve the overall health and well-being of children and youth.

Rajeev Singh Rathour, Radosław Smolec, Gergely Hajdu et al.

Classical Cepheids are not only excellent standard candles, but also invaluable tools to test stellar evolution and pulsation theories. Rates of their pulsation period change, quantified usually through $O-C$ diagrams, can be confronted with predictions of stellar evolution theory. On the other hand, period changes on much shorter time scales ($\sim$10$^{2}$-10$^{4}$days), attributed to non-evolutionary effects are often detected and lack detailed explanation. We aim to provide a systematic and quantitative description of irregular or non-linear period changes in Cepheids. We aim to provide a systematic and quantitative description of irregular or non-linear period changes in Cepheids. We analysed part of the OGLE data for classical Cepheids in the Magellanic Clouds (MCs; from both Large Magellanic Cloud, LMC, and the Small Magellanic Cloud, SMC) using the modified Hertzsprung $O-C$ technique. A sample of 3658 stars, with the best quality data and void of additional low-amplitude periodicities (e.g. due to non-radial pulsations), that could impact the results, was selected for analysis. Based on $O-C$ shapes, stars were classified into three categories: no period change (class 1), linear period change (class 2), and irregular change (class 3). In our investigation, $33.5\pm0.7$\% of analysed stars show irregular period changes. Considering the pulsation mode, irregular period changes were detected in $16.5\pm0.7$\% of the analysed fundamental mode stars and in $68.1\pm1.2$\% of the first overtone stars. The amplitude of variability in the $O-C$ diagrams increases with the pulsation period, and at a given pulsation period, it is larger for first overtone stars. While the increase is linear for first overtone stars, for fundamental mode stars it becomes steeper as the pulsation period increases.

Pradeep Kayshap, K. Murawski, Z. E. Musielak et al.

Waves are an integral part of the solar atmosphere, and their characteristics (e.g., dominant period, range of periods, power, and phase angle) change on a diverse spatio-temporal scale. It is well well-established observationally that the dominant periods of solar oscillations are 5-min and 3-min in the photosphere and chromosphere, respectively. This shows that the wave spectra and their dominant periods evolve between these two layers. We present observational results that demonstrate variations of the dominant period with heights in the photosphere and chromosphere. Six photospheric absorption lines and one chromospheric line are analyzed by using the IRIS data, and the Doppler velocity time series at seven different atmospheric heights are determined. The wavelet analysis is applied to these time series, and the resulting spectrum of wave periods and its dominant period are deduced at these heights, which gives height variations of the dominant period. The obtained data shows that the dominant period decreases with height, and that there are also changes in the range of wave periods within the spectrum. Numerical simulations of filtered wave spectra through the solar atmosphere are also performed, and the obtained results match the observational data.

Guangyou Zhu, Xi Li, Bin Zhao et al.

Abstract The 10 000‐m ultradeep dolomite reservoir holds significant potential as a successor field for future oil and gas exploration in China's marine craton basin. However, major challenges such as the genesis of dolomite, the formation time of high‐quality reservoirs, and the preservation mechanism of reservoirs have always limited exploration decision‐making. This research systematically elaborates on the genesis and reservoir‐forming mechanisms of Sinian–Cambrian dolomite, discussing the ancient marine environment where microorganisms and dolomite develop, which controls the formation of large‐scale Precambrian–Cambrian dolomite. The periodic changes in Mg isotopes and sedimentary cycles show that the thick‐layered dolomite is the result of different dolomitization processes superimposed on a spatiotemporal scale. Lattice defects and dolomite embryos can promote dolomitization. By simulating the dissolution of typical calcite and dolomite crystal faces in different solution systems and calculating their molecular weights, the essence of heterogeneous dissolution and pore formation on typical calcite and dolomite crystal faces was revealed, and the mechanism of dolomitization was also demonstrated. The properties of calcite and dolomite (104)/(110) grain boundaries and their dissolution mechanism in carbonate solution were revealed, showing the limiting factors of the dolomitization process and the preservation mechanism of deep buried dolomite reservoirs. The in situ laser U‐Pb isotope dating technique has demonstrated the timing of dolomitization and pore formation in ancient carbonate rocks. This research also proposed that dolomitization occurred during the quasi‐contemporaneous or shallow‐burial periods within 50 Ma after deposition and pores formed during the quasi‐contemporaneous to the early diagenetic periods. And it was clear that the quasi‐contemporaneous dolomitization was the key period for reservoir formation. The systematic characterization of the spatial distribution of the deepest dolomite reservoirs in multiple sets of the Sinian and the Cambrian in the Chinese craton basins provides an important basis for the distribution prediction of large‐scale dolomite reservoirs. It clarifies the targets for oil and gas exploration at depths over 10 000 m. The research on dolomite in this study will greatly promote China's ultradeep oil and gas exploration and lead the Chinese petroleum industry into a new era of 10 000‐m deep oil exploration.

J. I. Katz

Li {\it et al.\/} (2024) reported a 4.605 day period in the repeating FRB 20121102A in addition to the previously reported 157 day modulation of its activity. This note suggests that the shorter period is the orbital period of a mass-transferring star orbiting a black hole, possibly of intermediate mass, and that the 157 day period is the precession period of an accretion disc around the black hole. The mass-losing star must be evolved.

Stefan Kiefer, Andrew Ryzhikov

The period of a strongly connected digraph is the greatest common divisor of the lengths of all its cycles. The period of a digraph is the least common multiple of the periods of its strongly connected components. These notions play an important role in the theory of Markov chains and the analysis of powers of nonnegative matrices. While the time complexity of computing the period is well-understood, little is known about its space complexity. We show that the problem of computing the period of a digraph is NL-complete, even if all its cycles are contained in the same strongly connected component. However, if the digraph is strongly connected, we show that this problem becomes L-complete. For primitive digraphs (that is, strongly connected digraphs of period one), there always exists a number $m$ such that there is a path of length exactly $m$ between every two vertices. We show that computing the smallest such $m$, called the exponent of a digraph, is NL-complete. The exponent of a primitive digraph is a particular case of the index of convergence of a nonnegative matrix, which we also show to be computable in NL, and thus NL-complete.